In industrial materials and the like such as semiconductors typically, photolithography is generally used to perform micro fabrication. The photolithography is a technique for transferring or reprinting by radiating light, through a photomask, a photoresist applied on a silicon substrate thereby to perform reduced projection of a pattern of the photomask on the photoresist (see Non-Patent Citation 1). The photolithography makes it possible to produce wiring with fine diameters that had been impossible to make by conventional methods for processing parts in micro sizes.
For finer wirings, techniques to replace the techniques using light have been developed recently: a lithography techniques using an X ray (non-Patent citation 1), lithography techniques in which drawing is carried out by an electron beam directly (Non-Patent Citation 2, 3, and 4), lithography technique using an ion beam (non-Patent Citation 5), and the like techniques.
As they become capable of processing finer, these lithography techniques requires an exponential increase in an initial cost for an exposing apparatus itself. Moreover, some of the lithography techniques using masks face an increase in a cost of masks that make it possible to attain resolutions as much as the light wavelength to use.
In view of this, imprinting process has been remarked as a processing technique that attains a resolution of the order of 10 nm with low cost (Non-Patent Citation 6). The imprinting process is a processing technique for transferring a fine pattern of a mold on a resist by pressing the mold on the resist. The imprinting process makes it possible to perform microfabrication easily with low cost. With the imprinting process, a nano-scale structure can be formed quite easily.
Moreover, inventors of the present invention has already proposed a patterning method in which a poly-L-lysine layer is formed as a DNA immobilization layer on a glass substrate, and a DNA layer is immobilized on the DNA immobilization layer, and the DNA layer is patterned by imprinting process (Non-Patent Citation 7).
As an art in which a nucleic acid (typically DNA) is provided on a substrate, there is an attempt in for extending DNA straightly on a glass substrate by adding DNA in a gap between a pair of aluminum electrodes provided on the glass substrate and applying static electricity thereon (Non-Patent Citation 8). This technique, however, cannot form a pattern in a desired shape.
Furthermore, a micro contact printing method is also known (Non-Patent Citations 9 and 10). In the micro contact printing method, a stamp is prepared by transferring a micro-meter-sized pattern of a structure onto a rubber-like plastic, and molecules such as thiol or aminosilane, which forms a self-organizing film, are applied on surfaces of protrusions of the stamp. Then, the stamp is pressed against the substrate so as to form a patterned molecular film on the substrate by utilizing a chemical reaction between the molecules and the surface of the substrate. For example, in case where a molecular is formed using aminosilane, DNA is adsorbed to the molecular film if the DNA solution is applied onto the molecular film.
[Non-Patent Citation 1]
    Radiation Application Development Association: Radiation Application Research Database; data number 018015[Non-Patent Citation 2]    L. R. Harriot., S. D. Berger., C. Biddick., M. I. Blakey., S. W. Bowler., K. Brady., R. M. Camarda., W. F. Connelly., A. Crorken., J. Custy., R. Dimarco., R. C. Farrow., J. A. Felker., L. Fetter., R. Freeman., L. Hopkins., H. A. Huggins., C. S. Knurek., J. S. Kraus., J. A. Liddle., M. Mkrtychan., A. E. Novembre., M. L. Peabody., R. G. Tarascon., H. H. Wade., W. K. Waskiewicz., G. P. Watson., K. S. Werder and D. Windt., J. Vac. Sci. Tcchnol. B14(6), 3825-3828, 1996[Non-Patent Citation 3]    T. Yoshimura., H. Shiraishi., J. Yamamoto., and S. Okazaki., Appl. Phys. Lett. (63), 764-766, 1993[Non-Patent Citation 4]    J. Yamamoto., S. Uchino., T. Hattori., T. Yoshimura., and F. Murai., Jpn. J. Appl. Phys. (35), 6511-6516, 1996[Non-Patent Citation 5]    G. Gross., and R. Kaesmaier., J. Vac. Sci. Technol. B16(6), 1998[Non-Patent Citation 6]    Jun TANIGUCHI, Iwao MIYAMOTO, Masanori FURUMURO, and Shinji MATSUI, Journal of the Japan Society for Abrasive Technology, vol. 46, No. 6, 282-285, 2002[Non-Patent Citation 7]    Toshihito OTAKE, Kenichiro NAKAMATSU, Shinji MATSUI, Hitoshi TABATA, and Tomoji KAAI, The spring meeting of Jpn. Soci. of Appl. Phys. in 2004 (Mar. 30, 2004), Digest of the spring meeting in 2004, No, 3, p. 1503[Non-Patent Citation 8]    M. Ueda., H. Iwasaki., O. Kurosawa., and M. Washizu., Jpn. J. Appl. Phys. (38), 2118-2119, 1999[Non-Patent Citation 9]    R. Singhvi; A. Kumar; G. P. Lopez; G. N. Stephanopoulos; D. I. C. Wang; G. M. Whitesides; D. E. Ingber. Science, 1994, 264 (5159), 696-698.[Non-Patent Citation 10]    A. Kumar., H. A. Biebuyck., and G. Whitesides., Langmuir, (10), 1498-1511, 1994
As described above, various microfabrication techniques have been developed so far. However, these conventional techniques are not capable of patterning a biomaterial, namely, a nucleic acid (DNA or RNA) in a desired shape (desired pattern) on a substrate.
To begin with, the conventional techniques described in Non-Patent Citations 1 to 5 are discussed. The nucleic acid is a biomaterial and thus is not tolerant against radiation of x ray, electron beam, ion beam and the like, and may be denatured by an organic solvent. Therefore, the structure and function of the nucleic acid cannot be maintained in the conventional techniques described in Non-Patent Citations 1 to 5 in which x ray, electron beam, ion beam or the like is irradiated and an organic solvent is used.
On the other hand, the structure and function of the nucleic acid can be maintained by the methods described in Non-Patent Citations 6 to 9, which utilize DNA that is a biomaterial.
However, the method described in Non-Patent Citation 8 is merely capable of extending DNA on the substrate straightly, and cannot immobilize DNA in a desired pattern on the substrate.
In the methods described in Non-Patent Citations 9 and 10, the transfer of the molecules is carried out by pressuring the stamp onto the substrate in contact. Thus, it is not desirable for biomolecule such as DNA to employ such a process in which a load is applied on the molecules. Moreover, combinations of kinds of substrates and molecular films are limited because the molecular film is formed by the chemical reaction between the surface of the substrate and molecules. This gives a limitation to materials of the substrate on which the DNA film is formable.
Meanwhile, the method described in Non-Patent Citation 7 and proposed by the inventors of the present invention previously can perform the patterning in a desired pattern with DNA. However, the method described in Non-Patent Citation 7 uses a general imprinting process for imprinting DNA. Such as imprinting would possibly damage the structure and function of DNA by pressure, heat or light in imprinting.
The present invention was accomplished in view of the aforementioned problem. An object of the present invention is to provide a patterning method in which a self-organizing material such as a nucleic acid or the like having a self-organizing ability is immobilized in a predetermined pattern on a substrate by utilizing imprinting process, and a self-organizing material-patterned substrate in which the self-organizing material is patterned in a predetermined pattern, and a method of producing the self-organizing material-patterned substrate, and a photomask including the self-organizing material-patterned substrate.